The present invention relates to a loading cam apparatus incorporated in a toroidal type continuously variable transmission used as a transmission for an automobile, for example.
Toroidal type continuously variable transmission of a double cavity type used as a transmission for an automobile, for example, is configured as shown in FIG. 14. As shown in the figure, the toroidal type continuously variable transmission is provided with an input shaft 1 coupled to a driving source such as an engine or the like. The input shaft 1 is provided with a loading cam apparatus 2 so that the driving force is transmitted to a variator 3 through the loading cam apparatus 2. The variator 3 is provided with a driving force transmission shaft 4 which rotates and is interlocked with the loading cam apparatus 2 and the driving force transmission shaft 4 is provided with a pair of input disks 5a, 5b disposed so as to oppose each other. A pair of output disks 6a, 6b are coaxially disposed between the pair of the input disks 5a and 5b in a loosely fitted state with respect to the driving force transmission shaft 4 so that the output disks 6a and 6b rotate synchronously.
A plurality of power rollers 7 are provided between the input disks 5a, 5b and the output disks 6a, 6b so that the rollers roll in contact with the disks swangably. The output disks 6a, 6b are interlocked to each other through a loosely fitting shaft 8 which is loosely fitted to the driving force transmission shaft 4.
The variator 3 is arranged in a manner that the rotation driving force transmitted to the driving force transmission shaft 4 is further transmitted to the loosely fitting shaft 8 through the input disks 5a, 5b, the power rollers 7 and the output disks 6a, 6b, wherein a speed ratio, that is, a value obtained by dividing the rotation speed of the output disks 6a, 6b by the rotation speed of the input disks 5a, 5b is determined by the swing angle of the power rollers 7. In other words, the speed ratio is determined by a tilt angle of the displacement shafts rotatably supporting the ends of the power rollers 7.
To be more concrete, when the power rollers 7 lie along the level or horizontal direction in parallel to the driving force transmission shaft, the transmission is in a neutral state with the speed ratio of 1. When the output disks 6a, 6b sides of the power rollers 7 incline to the direction away from the driving force transmission shaft 4, the speed ratio decreases in accordance with the inclined angle. In contrast, when the output disks 6a, 6b sides of the power rollers 7 incline toward the driving force transmission shaft 4, the speed ratio increases in accordance with the inclined angle. A first gear 9 is fitted into the loosely fitting shaft 8 and further engages with a second gear 11 provided at a counter shaft 10.
The loading cam apparatus 2 is arranged to include a first cam surface 13 formed to have concave and convex portions thereon along a circumferential direction of one side surface of a loading cam 12 which engages with the input shaft 1 and rotates together with the input shaft 1, a second cam surface 14 formed to have concave and convex portions thereon along a circumferential direction of the rear surface of the input disk 5a, and a plurality of rollers 16 serving as rolling elements which are sandwiched between the first cam surface 13 and the second cam surface 14 in a state being held by a retainer 15 so as to be freely rolled.
As shown in FIGS. 13A and 13B, the retainer 15 is formed by a metal plate of a circular annular shape and integrally provided with a plurality of, for example, four convex portions 18 at the outer peripheral portions thereof along the circumferential direction thereof with a constant interval therebetween. A pocket 17 for holding the roller 16 is provided at each of the convex portions 18. Each of the pockets 17 is formed in a rectangular shape and the width and length allowances or tolerances thereof are preferably to be a space sufficient not for restricting the roller 16. That is, since the roller is restricted when the space is small, the space between the roller and the pocket is preferably in a range of about 0.05 to 0.5 mm. The symmetrical degree, positional degree and angular allowance of the four pockets 17 are required to be managed strictly to some extent in a view point of adjusting the phase between the cam surfaces and the pockets.
The retainer 15 of the loading cam apparatus 2 is manufactured by the cutting process and the pockets 17 are subjected to the induction hardening process. However, since the yield of the material of the retainer is not good and the cutting process takes a long time, the cost of the loading cam apparatus becomes expensive.
Further, since the induction hardening process is performed by abutting a coil to the convex portion 18, if the coil is not set suitably, the coil may touch the convex portion and so there arises a problem that the convex portion may be cracked or broken when the external force is applied to the touched portion.
In the case of performing the induction hardening process, the inner diameter portion as well as the four pockets 17 are required to be subjected to the hardening process. Furthermore, in the case of performing the induction hardening process, it is difficult to perform the hardening process at the pockets in particular since recesses are formed at the four corner portions of each of the pockets 17. Thus, since each of the pockets receives the centrifugal force of the roller 16 at the outer side thereof while receiving a large face pressure at the side walls, the stress applied to the four corner portions thereof becomes large, so that the hardness of the four corner portions having been subjected to the hardening process is low and so there arises a problem that the breakage occurs from the corner portions.
Each of the pockets 17 is usually formed in a manner that each of the four corner portions is designed to have the single radius R of less than 1 mm, so that the stress is likely concentrated at the corner portions. Further, since the coupling portion between the corner portion and the linear portion of the pocket is formed to be sharp, a burr or flash is likely generated at the coupling portion and so there arises a problem that the roller is likely restricted by the coupling portion at the time of assembling.
Accordingly, the present invention has been performed in order to obviate the aforesaid problems of the prior art.
An object of the present invention is to provide a retainer for a loading cam apparatus which is low in a carbon concentration and can be fabricated easily by the pressing process and so cost thereof can be reduced.
Another object of the present invention is to provide a loading cam apparatus wherein a space is partially formed between the boss portion of a loading cam and the retainer so that lubricating oil flows through the space on the cam surface of an input disk thereby to improve the lubrication property.
A further object of the present invention is to provide a loading cam apparatus wherein each of the four corner portions of a pocket is arranged to form a recess of arc shape and a coupling portion between the corner portion and a linear portion of the pocket is formed to have an obtuse angle thereby to avoid the concentration of stress at the corner portions, and a burr is scarcely generated at the time of stamping out the pocket by the pressing process.
A still further object of the present invention is to provide a loading cam apparatus wherein a step portion is formed between the boss portion of a loading cam and the retainer so as to partially form a space therebetween so that the contact area between the boss portion and the retainer is made smaller thereby to smoothly slide the retainer.
In order to attain the aforesaid object, according to an aspect of the present invention, there is provided with a loading cam apparatus for a toroidal type continuously variable transmission, which includes:
a first cam surface formed to have concave and convex portions thereon along a circumferential direction thereof;
a second cam surface formed to have concave and convex portions thereon along a circumferential direction thereof and to oppose to the first cam surface along an axial direction thereof;
a plurality of rolling elements sandwiched between the first cam surface and the second cam surface; and
a retainer for holding the plurality of rolling elements in a freely rotatable state, wherein the retainer includes,
a retainer main body of a circular annular shape, and
pockets provided at outer periphery portions of the retainer main body for holding the plurality of rolling elements, respectively, and wherein
the retainer main body is formed by carbonitriding material of iron system with a carbon concentration in a range from 0.02 to 0.20 wt % both inclusive
According to an example of the present invention, the retainer main body is formed by a pressing process.
According to an example of the present invention, each of the pockets includes
recesses of arc shape respectively provided at four corner portions of the pocket,
linear portions contacting to the rolling element, and
coupling portions each for coupling corresponding one of the recesses and corresponding one of the linear portions, wherein
each of the coupling portions is configured to have an obtuse angle larger than 90 degrees and smaller than 180 degrees where the obtuse angle is defined between a line extending along the one of said linear portions and a tangential line of the recess at an intersecting point between the corresponding one of said recesses and said corresponding one of said linear portions.
According to an example of the present invention, the first cam surface is formed on a loading cam, and wherein the retainer main body includes
a guide portion fitted into the loading cam,
outer diameter side projection portions provided at outer peripheral portions of the retainer main body to protrude on the second cam surface side, and
inner diameter side projection portions provided at inner peripheral portions of the guide portion to protrude on the second cam surface side, wherein
each of the inner diameter side projection portions is arranged to have a diameter larger than that of the guide portion thereby to form a step portion
According to an example of the present invention, the first cam surface is formed on a loading cam, the loading cam has a boss portion, and wherein the retainer main body includes
a guide portion fitted into the boss portion of the loading cam, and
a step portion provided at an inner periphery end of the guide portion to partially form a space between the boss portion of the loading cam and the step portion.
According to an example of the present invention, the retainer is formed by a metal plate, each of the pockets is provided with a projection portion protruding on both sides of the metal plate at an inner end side thereof, and the projection portions are formed by subjecting the metal plate to plasticity processing and disposed along a space between the first cam surface and the second cam surface along a circumferential direction of the retainer.
According to another aspect of the present invention, there is provided with a loading cam apparatus for a toroidal type continuously variable transmission which is provided at an input shaft coupled to a driving source and transmits driving force to an input disk, the loading cam apparatus rotates in interlocked with a driving force transmission shaft which is provided at the input disk, the loading cam apparatus comprising:
a first cam surface engaged with the input shaft and formed to have concave and convex portions on one surface of a loading cam rotating together with the input shaft along a circumferential direction thereof;
a second cam surface formed to have concave and convex portions on a rear surface of the input disk along a circumferential direction thereof;
a plurality of rolling elements sandwiched between the first cam surface and the second cam surface; and
a retainer for holding the plurality of rolling elements in a freely rotatable state, wherein the retainer includes,
a retainer main body of a circular annular shape, and
pockets provided at outer periphery portions of the retainer main body for holding the plurality of rolling elements, respectively, and wherein
the retainer main body is formed by carbonitriding material of iron system with a carbon concentration in a range from 0.02 to 0.20 wt % both inclusive.
According to an example of the present invention, each of the pockets includes
recesses of arc shape respectively provided at four corner portions of the pocket,
linear portions contacting to the rolling element, and
coupling portions each for coupling corresponding one of the recesses and corresponding one of the linear portions, wherein
each of the coupling portions is configured to have an obtuse angle larger than 90 degrees and smaller than 180 degrees where the obtuse angle is defined between a line extending along the one of said linear portions and a tangential line of the recess at a intersecting point between the corresponding one of the recesses and the corresponding one of the linear portions.
According to an example of the present invention, the retainer main body includes
a guide portion fitted into the loading cam,
outer diameter side projection portions provided at outer peripheral portions of the retainer main body to protrude on the second cam surface side, and
inner diameter side projection portions provided at inner peripheral portions of the guide portion to protrude on the second cam surface side, wherein
each of the inner diameter side projection portions is arranged to have a diameter larger than that of the guide portion thereby to form a step portion
According to an example of the present invention, the loading cam has a boss portion, and wherein the retainer main body includes
a guide portion fitted into the boss portion of the loading cam, and
a step portion provided at an inner periphery end of the guide portion to partially form a space between the boss portion of the loading cam and the step portion.
According to an example of the present invention, the retainer is formed by a metal plate, each of the pockets is provided with a projection portion protruding on both sides of the metal plate at an inner end side thereof, and the projection portions are formed by subjecting the metal plate to plasticity processing and disposed along a space between the first cam surface and the second cam surface along a circumferential direction of the retainer.
According to another aspect of the present invention, there is provided with a loading cam apparatus for a toroidal type continuously variable transmission which is provided at an input shaft coupled to a driving source and transmits driving force to an input disk, the loading cam apparatus rotates and is interlocked with a driving force transmission shaft which is provided at the input disk, the loading cam apparatus comprising:
a first cam surface engaged with the input shaft and formed to have concave and convex portions on one surface of a loading cam rotating together with the input shaft along a circumferential direction thereof;
a second cam surface formed to have concave and convex portions on a rear surface of the input disk along a circumferential direction thereof;
a plurality of rolling elements sandwiched between the first cam surface and the second cam surface; and
a retainer for holding the plurality of rolling elements in a freely rotatable state, wherein the retainer includes,
a retainer main body of a circular annular shape, and
pockets provided at outer periphery portions of the retainer main body for holding the plurality of rolling elements, respectively, and wherein
the retainer main body is formed by subjecting material of iron system with a carbon concentration in a range of 0.02 to 0.20 wt % or less to a pressing process and then subjecting the material thus pressed to a carbonitriding process.
As explained above, according to the present invention, since the retainer is made of soft material of iron system suitable for the pressing process, the pressing process can be performed easily. Further, since the entire surface of the retainer is carbonitrided, the hardness of the corner portions thereof at which the stress is concentrically applied can be increased advantageously.
According to the present invention, since the space is partially formed between the boss portion of the loading cam and the retainer due to the provision of the step portions, the lubricating oil flows through the space on the cam surfaces of the input disks thereby to improve the lubrication property of the retainer.
According to the present invention, since each of the four corner portions of the pocket is arranged to form the recess of arc shape and the coupling portion between the corner portion and the linear portion of the pocket is formed to have the obtuse angle, the concentration of stress at the corner portions can be avoided, and a burr is scarcely generated at the time of stamping out the pocket by the pressing process.
According to the present invention, since the step portion is formed between the boss portion of the loading cam and the retainer so as to partially form the space therebetween, the contact area between the boss portion and the retainer is made smaller thereby to smoothly slide the retainer.
According to the loading cam apparatus of the present invention, even if a first cam surface separates largely from a second cam surface, the retainer is held at the center portion between the both cam surfaces without deviating therefrom due to the presence of projection portions provided at both sides of the retainer so as to oppose to the both cam surfaces, respectively. Thus, rolling elements can be prevented from completely coming out of the pockets of the retainer and the corner portions of the pockets are prevented from contacting to the rolling contact surfaces of the rolling elements. Further, the deviation of the lubrication property between the rolling elements and the respective cam surfaces can be suppressed. Furthermore, even if a projection portion is provided at the rolling element, the rolling element can be housed at the inside of the pocket.